Normally, fluid valve structure applications occur in environments where the pressure is less than about 1000 psi (68.95 Bars) and the temperature of the fluid is less than about 200.degree. Fahrenheit (94.degree. Celsius). However, certain applications of fluid valves require use in high pressure and high temperture environments. As an example, in the control of boiler feed water in power generating plants there is a requirement for fluid valves operating in pressures around 7200 psi (496 Bars) and in temperature ranges of around 450.degree. Fahrenheit (232.degree. Celsius). Normally, valves operating in such pressure and temperature extremes use graphite packing material rather than TFE (tetrafluorethylene) packing material due to the limiting usage of TFE at the elevated temperatures and pressure. The use of graphite packing leads to increased valve stem friction as the valve stem strokes through the packing thereby severely limiting valve operation and leading to increased wear on the packing material.
However, prior attempts to utilize TFE packing at the elevated pressure and temperature ranges was normally not recommended nor found feasible. In such attempts, it was found that the TFE packing material extruded due to the severe pressures and sliding movement of the valve stem which tended to remove the material from the packing in long strands of string-like extrusions. Eventually, the continued removal and extruding of material from the packing led to a loss of sealing ability for the packing and thereby requiring early replacement of the packing material and possibly the valve stem itself.
Accordingly, it is desired to provide an improved valve stem packing containment for use in high pressure, high temperature conditions which can provide reliable service with a minimum of friction between the sliding valve stem and the packing material and with a minimum of service required. It is also desired that a valve stem packing containment be provided which can extend the useful valve life even in non-elevated pressure and temperature conditions.